HRESULT 0x80090343 (SEC_E_UNSUPPORTED

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Constant name:

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Description:

An unsupported preauthentication mechanism was presented to the Kerberos package.

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SEC_E_KDC_UNKNOWN_ETYPE	SEC_E_DELEGATION_REQUIRED

SEC_E_UNSUPPORTED_PREAUTH

SEC_E_UNSUPPORTED_PREAUTH signals this condition: Kerberos received a preauthentication mechanism it does not support. The preauthentication method offered by the client or intermediary is unsupported by the Kerberos package or domain configuration. This can arise from an outdated client, incompatible certificate path, or inconsistent policy.

What to check

Identify whether the flow is password, smart card, certificate, or another Kerberos preauthentication path.
Review KDC and client events for the exact mechanism and principal involved.
Update or reconfigure the incompatible component rather than disabling preauthentication controls globally.

Microsoft: SSPI status codes

Microsoft: Kerberos authentication troubleshooting

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